Outdoor Allergens: Nature's Triggers

Outdoor allergens are an important part of the exposures that lead to allergic disease. Primary sources for outdoor allergens include vascular plants (pollen, fern spores, soy dust), and fungi (spores, hyphae). They are often seasonal and commonly inhaled as pollen or spores. Additional triggers could be insect stings from bees or wasps, and irritants like smoke or pollution.

Pollen

Pollen is one of the most common triggers of seasonal allergies. Many people know pollen allergy as hay fever. Experts usually refer to pollen allergy as seasonal allergic rhinitis. For those with an allergy, pollen triggers the antibody immunoglobulin E, which creates mucus and leads to symptoms such as congestion and sneezing.

Pollen is a powdery, granular substance found in the flowers of trees, grasses, and weeds, which plays a crucial role in plant fertilization. It can be spread either by insects or wind. Flowering plants that rely on insects for pollination, such as roses, cherry trees, and pear trees, typically do not cause allergic rhinitis. However, many plants produce powdery pollen that is easily carried by the wind. These plants are the primary culprits behind allergy symptoms.

Each plant has a period of pollination that does not vary much from year to year. Depending on the time of year, the type of pollen in the air will be different. There are around 30 different types of pollen that cause hay fever and it is possible to be allergic to more than one type. Tree pollen tends to be released during spring, and grass pollen is common in late spring and early summer. Weed pollen can be released at any time from early spring to late autumn. Moreover, in warmer places, pollination can occur year-round.

Hay fever symptoms usually appear when the pollen count, which is a measure of the number of grains of pollen in one cubic meter of air, exceeds 50. The weather conditions affect how much pollen is released and spread around. On humid and windy days, pollen spreads easily but on rainy days, pollen can be cleared from the air. On sunny days, the pollen count is highest in the early evening when hay fever symptoms are most likely to appear.

Insect

An insect allergy is characterized by the development of allergic reaction symptoms following an insect sting or bite. The severity of reactions to insect bites and stings varies among individuals. Some individuals may experience mild to moderate allergic symptoms, whereas others may exhibit a severe allergic reaction, such as anaphylaxis.

There are many different kinds of insects or "insect-like bugs" that can cause an allergic reaction, including both stinging insects and biting insects.

Bees, wasps, hornets, yellow jackets and fire ants are the most common stinging insects that cause an allergic reaction. When these insects sting you, they inject a toxic substance called venom. Most people stung by these insects recover within hours or days. In others, this venom can trigger a life-threatening allergic reaction.

Mosquitoes, kissing bugs, bedbugs, fleas and certain flies are the most common biting insects known to cause an allergic reaction. Most people bitten by insects suffer pain, redness, itching, stinging and minor swelling in the area around the bite. Rarely, insect bites may trigger a life-threatening allergic reaction.